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Date:   Sat, 19 Mar 2022 11:04:43 +0100
From:   Florian Westphal <fw@strlen.de>
To:     zhouzhouyi@gmail.com
Cc:     edumazet@google.com, davem@davemloft.net, yoshfuji@linux-ipv6.org,
        dsahern@kernel.org, kuba@kernel.org, pabeni@redhat.com,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Wei Xu <xuweihf@ustc.edu.cn>
Subject: Re: [PATCH] net:ipv4: send an ack when seg.ack > snd.nxt
Message-ID: <20220319100443.GA13956@breakpoint.cc>
References: <20220319090142.137998-1-zhouzhouyi@gmail.com>
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zhouzhouyi@gmail.com <zhouzhouyi@gmail.com> wrote:
> -	if (after(ack, tp->snd_nxt))
> +	if (after(ack, tp->snd_nxt)) {
> +		tcp_send_ack(sk);
>  		return -1;
> +	}

If we really need to do this we need to
  if (!(flag & FLAG_NO_CHALLENGE_ACK))
	tcp_send_challenge_ack(sk);

... else this might result in two acks?
Whats the problem thats being fixed here?